Method for manufacturing semiconductor element

ABSTRACT

A method for manufacturing a semiconductor element is provided. The method includes providing a semiconductor wafer including a substrate and a semiconductor structure on the substrate, forming a cleavage starting portion in the semiconductor wafer, and dividing the semiconductor wafer into a plurality of semiconductor elements by transferring a pressing member on the semiconductor wafer in a state where the pressing member is pressed against the semiconductor wafer to separate the semiconductor wafer at the cleavage starting portion. The pressing member includes a tip portion to be pressed on the semiconductor wafer, and the tip portion has a spherical surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2015-131776 filed on Jun. 30, 2015. The entire disclosure of JapanesePatent Application No. 2015-131776 is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to a method for manufacturing asemiconductor element.

2. Description of Related Art

Light-emitting elements have been widespread as various light sources.In particular, semiconductor light-emitting elements typified bylight-emitting diodes (LED) or laser diodes (LD) have advantages such asreduction in size, low power consumption, and a long life, and thus haveachieved great proliferation. The semiconductor light-emitting elementsare generally manufactured through steps in which, after a semiconductorlayer is grown on a growth substrate, a semiconductor wafer obtained iscleaved (e.g., by scribing and breaking) into chips.

Break blades have been known as members for pressing the semiconductorwafer in the breaking described above. The break blades are formed, forexample, in a size of which the break blades can traverse thesemiconductor wafer. In the case where LED chips (dice), which arelight-emitting elements cleaved from the semiconductor wafer, are to beformed to have a rectangular shape, a scribe line is formed in astraight line and the semiconductor wafer can be broken by use of thebreak blades.

However, for example, in the case where the light-emitting elements areto be formed in a hexagonal shape, the scribe line is bent in thesemiconductor wafer. In this case, if a cleaving member that linearlycleaves the semiconductor wafer, such as the break blade, is used,pressing against the wafer at portions except for the scribe line maydamage the light emitting element. In the case where the break blade ispressed against the semiconductor wafer, there is no choice but toprovide a damage area in advance and linearly cleave the semiconductorwafer, or to carefully position a small blade, of which the size is thesame as that of the light-emitting element. In any case, operationsbecome so complicated. Thus, in the case where the shape of thelight-emitting elements is not rectangular, it takes time to positionthe blade during a cleaving operation, which may cause a disadvantage inmanufacturing. See Japanese Unexamined Patent Application PublicationNo. H10-074712, Japanese Unexamined Patent Application Publication No.2006-135309, Japanese Unexamined Patent Application Publication No.2004-349623, and Japanese Unexamined Patent Application Publication No.2012-124300.

One of the objects of the present disclosure is to provide a method formanufacturing a semiconductor element, which is suitable formanufacturing a semiconductor element such as a light-emitting elementhaving in a non-rectangular shape.

SUMMARY

According to an embodiment of the present disclosure, a method isprovided for manufacturing a semiconductor element having a shape of apolygon having five or more angles in a plan view. The method includesproviding a semiconductor wafer including a substrate and asemiconductor structure on the substrate, forming a cleavage startingportion in the semiconductor wafer, and dividing the semiconductor waferinto a plurality of semiconductor elements by transferring a pressingmember on the semiconductor wafer in a state where the pressing memberis pressed against the semiconductor wafer to separate the semiconductorwafer at the cleavage starting portion. The pressing member includes atip portion having a curved surface to be pressed on the semiconductorwafer.

According to the aforementioned embodiment, even in the case ofpolygonal semiconductor elements, it is possible to efficiently cleavethe semiconductor wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a light-emittingelement according to a first embodiment.

FIG. 2 is a schematic flowchart illustrating a method for manufacturingthe light-emitting element in FIG. 1.

FIG. 3 is a schematic plan view illustrating a semiconductor wafer.

FIG. 4 is a schematic cross-sectional view illustrating an example inwhich a laser beam is irradiated to an interior of the semiconductorwafer to perform laser scribing.

FIG. 5 is a schematic enlarged view of a main part illustrating anexample in which a cleavage starting portion is formed in thesemiconductor wafer in FIG. 3.

FIG. 6 is a schematic cross-sectional view illustrating a situation inwhich the semiconductor wafer is cleaved with a pressing member.

FIG. 7 is a schematic enlarged cross-sectional view of a main part inFIG. 6.

FIG. 8 is a schematic enlarged cross-sectional view of a main partillustrating a relationship between an outer diameter of a tip portionof the pressing member and the light-emitting element.

FIG. 9 is a schematic enlarged cross-sectional view of a main partillustrating a state in which a surface of the semiconductor wafer to bepressed is pressed with the tip portion of the pressing member.

FIG. 10 is a schematic cross-sectional view of a state in which thesemiconductor wafer is set on a ring-shaped frame according to variantexample.

FIG. 11 is a schematic plan view illustrating a scanning pattern inwhich the pressing member is scanned on the semiconductor wafer.

FIG. 12 is a schematic plan view illustrating a scanning patternaccording to a second embodiment, in which the pressing member isscanned on the semiconductor wafer.

FIGS. 13A and 13B are schematic plan views illustrating a backgroundcleaving method.

DETAILED DESCRIPTION

First, the outline of a light-emitting element 10 obtained by amanufacturing method according to the embodiment of the presentdisclosure will be described. The light-emitting element 10 is oneexample of a semiconductor element.

FIG. 1 illustrates the cross section of the light-emitting element 10.As illustrated in FIG. 1, in the light-emitting element 10, nitridesemiconductor layers that serve as a semiconductor structure 11 arestacked on a first main surface 5 a, which is one main surface of asubstrate 5. More specifically, in the light-emitting element 10, thesemiconductor structure 11 that includes an n-side semiconductor layeras a first conductive side semiconductor layer 6, an active layer 8, anda p-side semiconductor layer as a second conductive side semiconductorlayer 7 is stacked in this order on side of a front surface, which isthe first main surface 5 a of the substrate 5 including a pair of mainsurfaces opposite to each other. Also, an n-side pad electrode 3A iselectrically connected to the n-side semiconductor layer, and a p-sidepad electrode 3B is electrically connected to the p-side semiconductorlayer. When power is supplied from outside to the light-emitting element10 via the n-side pad electrode 3A and the p-side pad electrode 3B,light is emitted from the active layer 8, and the light is mainlyextracted from the second conductive side semiconductor layer 7 inFIG. 1. That is, in the light-emitting element 10 in FIG. 1, a side of asurface on which a pair of positive and negative electrodes 3 (inclusiveof the n-side pad electrode 3A and the p-side pad electrode 3B) areformed (i.e., upper side in FIG. 1) serves as a main light extractionsurface 18. The active layer 8 corresponds to a light emission layer.The central wavelength of light emitted from the active layer 8 is in arange of, for example, from 360 nm to 650 nm.

Also, light-transmissive conductive layers 13 are respectively formed onthe n-side semiconductor layer and the p-side semiconductor layer, andthe n-side pad electrode 3A and the p-side pad electrode 3B arerespectively formed on the light-transmissive conductive layers 13.Furthermore, only predetermined portions of surfaces of the n-side padelectrode 3A and the p-side pad electrode 3B are exposed from aprotective film 14 having insulation properties, and other portions ofthe surfaces are covered with the protective film 14.

The substrate 5 is made of, for example, sapphire, and the semiconductorstructure 11 is made of, for example, nitride semiconductors such asGaN. Also, the light-transmissive conductive layers 13 may be omitted.The light-emitting element 10 illustrated in FIG. 1 is a so-calledface-up type light-emitting element in which the side of secondconductive side semiconductor layer 7 serves as the light extractionsurface, and the side of the second main surface 5 b serves as amounting surface. A light-emitting element may be manufactured to be aso-called face-down type light-emitting element in which the side of thesecond main surface 5 b serves as the light extraction surface, and theside of second conductive side semiconductor layer 7 serves as themounting surface.

Method for Manufacturing Light-Emitting Element According to FirstEmbodiment

Hereinafter, the method for manufacturing the light-emitting element 10above will be described referring to a flowchart in FIG. 2 and FIGS. 3to 9.

Providing Semiconductor Wafer

First, a semiconductor wafer is provided at Step S21 in FIG. 2. Asillustrated in FIG. 3, a semiconductor wafer 20 has an approximatelycircular shape in a plan view, and includes an orientation flat surfaceOL at a portion thereof. The semiconductor wafer 20 includes thesubstrate 5 and the semiconductor structure 11 arranged on the substrate5. The diameter of the semiconductor wafer 20 can be in a range of, forexample, approximately 50 to 100 mm. Also, the number of light-emittingelements obtained from one semiconductor wafer is in a range of, forexample, approximately 1500 to 200000.

Forming Cleavage Starting Portion 22

Next, a cleavage starting portion 22 is formed in the semiconductorwafer 20 at Step S22 in FIG. 2. The cleavage starting portion 22 is aportion that serves as a guide for facilitating the cleavage of thesemiconductor wafer 20 in order to divide the semiconductor wafer 20into pieces each having a predetermined size to obtain thelight-emitting elements, and typically corresponds to the scribe line.However, the cleavage starting portion 22 is not required to be acontinuous straight form; the cleavage starting portion 22 can beconstituted of patterns of a wavy form or discrete patterns such as adotted form. Also, the cleavage starting portion 22 includes a fragilearea formed in the interior of the semiconductor wafer, in addition togrooves physically formed in a surface of the semiconductor wafer.Preferably, the cleavage starting portion 22 is formed by irradiating alaser beam. A cross-sectional view of FIG. 4 illustrates an example inwhich a laser beam LB is irradiated to the interior of the semiconductorwafer 20 to perform laser scribing. According to such laser scribing,the laser beam is scanned on the semiconductor wafer 20, so that thecleavage starting portion 22 can be formed in a desired pattern. It isnoted that, while the cleavage starting portion 22 is represented as aline existing in the interior of the semiconductor wafer 20 in FIG. 4,normally, it is considered that the cleavage starting portion 22 isgenerated only in the interior (only in the vicinity of convergenceposition of a laser beam) of the semiconductor wafer 20 immediatelyafter the laser beam is irradiated, and that a crack is graduallyexpanded in a thickness direction (i.e., up-and-down direction) of thewafer, starting from the cleavage starting portion 22.

Also, the cleavage starting portion 22 may be provided on both surfacesof the semiconductor wafer, and preferably, formed so as to reach asurface opposite to a surface on which the semiconductor structure isformed, that is, a back surface (a second main surface 5 b) of thesubstrate 5. This formation has an advantage such that the cleavage ofthe semiconductor wafer can be easily performed. Also, arranging theportion on which the laser beam focused to be away from thesemiconductor structure 11 can avoid a situation in which thesemiconductor structure 11 (in particular, the active layer 8) isdamaged by the laser beam. Specifically, as illustrated in thecross-sectional view in FIG. 4, the laser beam is irradiated from theside of a back surface BS of the semiconductor wafer 20 (substrate 5),so that the cleavage starting portion 22 is formed.

Preferably, with use of the laser beam having wavelengths that canpenetrate the substrate 5, the cleavage starting portion 22 is formed byfocusing the laser beam in the interior of the substrate 5. Thesubstrate 5 is, for example, a sapphire substrate, and examples of theenergy per pulse (pulse energy), the frequency, the pulse width, and thewavelength of the laser beam are in ranges of 0.8 to 5 μl, 50 to 200kHz, 300 to 50000 fs (femtosecond), and 500 to 1100 nm, respectively.When the laser beam is irradiated to the interior of the substrate 5with pulse drive, the crack is expanded from a portion on which thelaser beam is focused or in the vicinity of the portion on which thelaser beam is focused. For example, the portion on which the laser beamis focused is set close to the side of the back surface (the side of thesecond main surface 5 b) of the substrate 5, which causes the crack toreach the back surface of the substrate 5. Accordingly, when viewed fromthe side of the back surface of the substrate 5, it is possible that thecrack is connected in almost all the paths on which the laser beam isscanned, but the crack does not reach the surface on the side oppositeto the back surface (the side where the semiconductor structure 11 ofthe semiconductor wafer 20 is formed). Cleaving is performed withrespect to the semiconductor wafer 20 in the aforementioned state, whichallows for cleaving the semiconductor wafer 20 with accuracy.

It is preferable that the cleavage starting portion 22 be formed up to aportion near the semiconductor structure 11. For example, it ispreferable that the cleavage starting portion 22, which is formed so asto reach the back surface BS of the substrate 5, extend in a depthdirection (i.e., the thickness direction of the semiconductor wafer 20),and that one end of the cleavage starting portion 22 reaches the portionnear the semiconductor structure 11. With this arrangement, thethickness of the portion to be cleaved in the cleaving can be reduced,thereby facilitating the cleaving. However, in the present disclosure,it is not necessary for all the cleavage starting portions to reach theportion near the semiconductor structure 11, and even in the case wherea portion of the cleavage starting portion 22 does not reach the portionnear the semiconductor structure 11, it is sufficient that the cleavagestarting portion 22 be formed such that the cleavage is sufficientlyperformed. For example, a distance of the cleavage starting portion 22from the semiconductor structure 11 is in a range of 0 to 10 μm. Aportion of the cleavage starting portion 22 may penetrate thesemiconductor structure 11 and reach the surface of the semiconductorwafer 20, but it is preferable that the cleavage starting portion 22 donot penetrate the semiconductor structure 11 until the cleaving isperformed. This is because, if the semiconductor structure 11 iscompletely divided, the semiconductor wafer may be cut into theindividual light-emitting elements and may be scattered before startingthe cleaving. To which portion the cleavage starting portion 22 extendscan be adjusted based on scribing conditions or waiting time subsequentto the scribing. Also, the portion on which the laser beam is irradiatedin the interior of the substrate 5, for example, is located within 150μm from the semiconductor structure 11.

The pattern of the cleavage starting portion 22 formed in thesemiconductor wafer 20 defines the shape of the light-emitting elementsto be obtained by the cleavage. Preferably, the shape of thelight-emitting elements in a plan view is a polygon having five or moreangles. Generally, the shape of the light-emitting elements is aquadrangle (typically, a square or rectangle). However, in view ofcombining a lens or the like and the light-emitting elements or in viewof the emission area of output light, it can be considered that theshape of the light-emitting elements be preferably a circle. In the casewhere the light-emitting elements are circular, processing of thesemiconductor wafer for the cleavage is difficult, and further, in thecase where a plurality of circular light-emitting elements are cut outfrom the semiconductor wafer, unused regions are formed between thecircular light-emitting elements adjacent to each other. Accordingly,the amount of light-emitting elements obtained from one semiconductorwafer, that is, an available area of the semiconductor wafer that can beused for light emitting elements is decreased, which may reduce yields.In view of this, in the case where the shape of plan view of thelight-emitting elements is a polygon having five or more angles, theshape of the light-emitting elements in a plan view can be approximatedto a circle while wasteful areas of the semiconductor wafer are reduced,so that improvements to obtain the output light of a higher quality canbe expected.

Preferably, as illustrated in FIG. 5, the patterns of the cleavagestarting portion 22 are formed in the semiconductor wafer 20 so that theshape of each light-emitting element in a plan view is a hexagonalshape. Accordingly, the cleavage starting portion 22 is a polygonal linein a plan view of the semiconductor wafer 20. It is noted that, in thepresent disclosure, the patterns of the cleavage starting portion arenot limited to the polygonal line, and a cleaving method described latercan be applied to the cleavage starting portion formed in a straightline or curved line. In order to reduce the wasteful areas of thesemiconductor wafer as much as possible, areas to be the light-emittingelements may be arranged in the wafer so as to allow tessellation. Forexample, the shape of the light-emitting elements in a plan view isformed in a regular hexagon whose one side has a length of D₆ and theregular hexagons are arranged in a honeycomb pattern.

In the case where the shape of the light-emitting elements in a planview is a hexagon, it is preferable that the substrate 5 having thecrystal structure having hexagonal crystal system be used. All thecleavage starting portions 22 may be formed along the cleavage plane(for example, m-plane of sapphire) of the substrate 5, or all thecleavage starting portions 22 may be formed so as to be shifted from thecleavage plane of the substrate 5. With this, cleavage properties ofeach side of the light-emitting element can be uniform. Examples of thesubstrate 5 having the crystal structure of hexagonal crystal systeminclude, for example, a sapphire substrate and a GaN substrate.Normally, the easiness of cleaving the substrate 5 is approximatelyequal to the easiness of cleaving the semiconductor wafer 20, becausemost of the thickness of the semiconductor wafer 20 is occupied by thesubstrate 5. In the case where most of the thickness of thesemiconductor wafer is occupied by members except for the substrate 5,such as the semiconductor structure, the members may be formed ofmaterials having the crystal structure of hexagonal crystal system.

The cleavage starting portion 22 refers to a portion that serves as astarting point of the cleavage in the later-described step of cleavinginto the light-emitting elements and indicates a crack generated in thesemiconductor wafer before the step of cleaving. The cleavage startingportion 22 can be formed with cutter scribing, but laser scribing usingthe aforementioned laser beam is suitable for forming the cleavagestarting portion having polygonal line patterns.

Cleaving into Light-Emitting Element

At Step S23 in FIG. 2, the semiconductor wafer 20 is cleaved with use ofthe cleavage starting portion 22 so as to cut the semiconductor wafer 20into the individual light-emitting elements. More specifically, asillustrated in cross-sectional views in FIGS. 6 to 9, a pressing member30 is transferred on the semiconductor wafer 20 while being pressedagainst the semiconductor wafer 20, and the semiconductor wafer 20 isdivided on the cleavage starting portion 22 and cleaved into theindividual light-emitting elements. A scanning controller 33 performs atransfer in the vertical direction, in which the pressing member 30 ismoved upward and downward so that a tip portion 31 of the pressingmember 30 contacts and separate from the surface of the semiconductorwafer 20 to be pressed, and a transfer in the horizontal direction, inwhich the pressing member 30 is scanned on a surface of thesemiconductor wafer 20. That is, a device for manufacturing thelight-emitting elements includes the pressing member 30 and the scanningcontroller 33 that controls the transfer of the pressing member 30.

The case where the side of the semiconductor wafer 20 is fixed, and theside of the pressing member 30 is transferred has been described in theexample above. However, the transfer of the semiconductor wafer and thepressing member can be a relative transfer, and for example, it may besuch that the pressing member is fixed, and the semiconductor wafer istransferred. Furthermore, the present disclosure is not limited to amode in which any one of the semiconductor wafer and the pressing memberis fixed, but relative transfer between the semiconductor wafer and thepressing member may be achieved by transferring both of thesemiconductor wafer and the pressing member. For example, it may beconstituted such that transfer is divided into X, Y, and Z directions,and the transfer in a X-Y plane is performed by the pressing member, andthe transfer in the Z direction is performed by the semiconductor wafer.

Pressing Member 30

In the pressing member 30, the tip portion 31 to be pressed against thesemiconductor wafer 20 is a curved surface. With this arrangement, whilestress acts on the cleavage starting portion 22, damage on thesemiconductor wafer 20 can be reduced. Also, even in the case ofcleaving into the light-emitting elements each having a polygonal shape,it is possible to efficiently cleave the semiconductor wafer 20. Thatis, in the case where the light-emitting elements has a quadrangularshape as in background arts, the scribe line drawn on the semiconductorwafer is linearly formed, and therefore, as illustrated in FIGS. 13A and13B, breaking of the wafer can be performed along the linear scribeline. However, in the case where the scribe line is bent as illustratedin FIG. 5, the breaking may not easily be performed. For example, in thecase where a cleaving member that linearly cleaves an object, such as abreak blade, is used, a dice might be damaged when portions other thanthe scribe line are pressed. In the case where the semiconductor waferis pressed with the break blade, it may be necessary to predetermine adamage area and linearly cleave the semiconductor wafer, or carefullyposition a small blade, the size of which is the same as that of thedice.

Accordingly, as described above, the tip portion 31 of the pressingmember 30 has a curved surface. When the semiconductor wafer 20 ispressed with this tip portion 31 having a curved surface, which has aconvex shape facing the side of the semiconductor wafer 20, thesemiconductor wafer 20 is warped and cleaved. With this manner, thenecessity of the exact positioning of the pressing member as inbackground techniques can be eliminated. Furthermore, even in the casewhere the scribe line, that is, the cleavage starting portion 22, isbent in a plan view, the semiconductor wafer can be cut into individualpieces having a shape corresponding to the cleavage starting portion 22without providing the damage area, and cleaving of the semiconductorwafer into the polygonal light-emitting elements can be efficientlyperformed.

For example, stainless steel or zirconia can be used for the materialsof the pressing member 30. Also, it is preferable that the tip portion31 of the pressing member 30 has a curved surface. Accordingly, whilestress acts on the cleavage starting portion 22, damage on thesemiconductor wafer 20 can be avoided. It is preferable that the tipportion 31 of the pressing member 30 have a spherical surface. It isnoted that, in the present specification, the “spherical surface” doesnot mean the entire surface of a spherical body, but means a portion ofthe spherical body. For example, in order that the tip portion 31 of thepressing member 30 has the spherical surface, the shape of the tipportion 31 can be a semispherical shape. Also, the tip portion 31 may beconstituted of a spherical body. For example, it may be such that thespherical body is fixed on a holder, and the semiconductor wafer 20 ispressed with the spherical body. By use of the tip portion 31 having aspherical surface, the semiconductor wafer 20 can be pressed in an areawhose shape is similar to a point. The shape of the tip portion 31 maybe an elliptical surface except for the spherical surface.

In the present embodiment, the outer diameter D₁ of the tip portion 31is longer than the diameter of the circumscribed circle of the shape ofthe light-emitting element in a plan view. Preferably, the outerdiameter D₁ of the tip portion 31 is two times as long as the diameterof the circumscribed circle of the shape of the light-emitting elementin a plan view or more. Also, the outer diameter D₁ of the tip portion31 is, for example, less than the diameter of the semiconductor wafer20.

It is preferable that the curvature of the tip portion 31 be larger thanthat of a curved surface that can press the whole of the semiconductorwafer 20 at once. That is, it is preferable that the curvature radius ofthe tip portion 31 be smaller than that of the curved surface that canpress the whole of the semiconductor wafer 20 at once. An increase incurvature (i.e., a decrease in curvature radius) can lead to an increasein deflection of the semiconductor wafer 20, so that favorable cleavingof the semiconductor wafer 20 can be performed. The curvature radius ofthe tip portion 31 can be, for example, in a range of 2 to 20 mm. Also,the curvature radius of the tip portion 31 may be 2 to 25 times largerthan that of one side of the shape of the light-emitting element in aplan view. Preferably, the tip portion 31 has a size that allows the tipportion 31 to simultaneously press the right and left of the cleavagestarting portion 22, which are to be breaking positions, without failingwhen the pressing member 30 presses any portion of the main surface ofthe semiconductor wafer 20, as illustrated in FIGS. 7 and 8. In the casewhere the outer diameter D₁ of the tip portion 31 is smaller than theouter diameter D₂ of the light-emitting element, the light-emittingelement only on one side of the cleavage starting portion 22 is possiblypressed, which might cause cleavage failure. Accordingly, it ispreferable that the outer diameter D₁ of the spherical surface of thetip portion 31 be larger than the outer diameter D₂ of thelight-emitting element. For example, in the case where thelight-emitting element has a hexagon, a distance between verticesopposite to each other with respect to the center of the hexagoncorresponds to the outer diameter D₂ of the light-emitting element. Withthis shape, in the case where the tip portion 31 contacts any portion ofthe light-emitting element, it is possible for the tip portion 31 toinfallibly press an area inclusive of both sides of the cleavagestarting portion 22. Then, determining the amount of indentation by thepressing member 30 so as to perform pressing in the aforementionedmanner allows for performing the cleavage reliably. The outer diameterD₁ of the tip portion 31 can be, for example, approximately from 5 to 30times the outer diameter D₂ of the light-emitting element.

The tip portion 31 refers to a portion including a surface of thepressing member 30 which can press the semiconductor wafer 20. When thepressing against the semiconductor wafer 20 is performed, it ispreferable that the tip portion 31 presses the semiconductor wafer 20 atan extremely tiny area approximating to a point. With this, the cleavagecan be easily performed with a small force. Also, as described above, itis preferable that the shape (the outer diameter, curvature, and thelike) of the tip portion 31 and the amount of the indentation of thepressing member 30 be selected so that the two or more light-emittingelements adjacent to each other can be simultaneously pressed. With thisarrangement, the pressing member 30 can be scanned in a state where thetip portion 31 continuously presses the two or more light-emittingelements, so that the cleavage can be efficiently performed. That is, ina state where the tip portion 31 presses only one light-emittingelement, the pressed light-emitting element is slightly sunk and it maybe difficult to perform the cleavage. Pushing two or more light emittingelements can avoid such state. Similar arrangement can be applied to thecase where a protective sheet 52 described later is arranged, and thesemiconductor wafer 20 is pressed in the area approximate to a point,with the pressing member 30 through the protective sheet 52.

It is preferable that the tip portion 31 of the pressing member 30presses against the side of the back surface BS of the substrate 5 tocleave the semiconductor wafer 20. Thus, the surface of thesemiconductor wafer 20 to be pressed serves as a surface that isdifferent from the growth surface of the substrate 5, which can reducethe possibility of the damage of the semiconductor structure.

As described above, it is preferable that the cleavage starting portion22 be formed so as to reach the surface of the semiconductor wafer 20 tobe pressed. Then, as illustrated in FIG. 7, which is a schematicenlarged cross-sectional view of a main part in FIG. 6, it is preferablethat semiconductor wafer 20 be pressed from the side where the cleavagestarting portion 22 is provided (i.e., side of the surface where thecleavage starting portion 22 reaches). In this manner, the cleavage canbe progressed from the cleavage starting portion 22 with a small amountof indentation compared with the case where the semiconductor wafer 20is pressed from the opposite side, which can divide the semiconductorwafer 20 into the light-emitting elements. In this time, an uncutportion to be cleaved has a thickness such that the uncut portion can becleaved with a small amount of indentation, and the thickness can be,for example, equal to or less than 150 μm, depending on a size of thelight emitting element. More preferably, as described above, thecleavage starting portion 22 is formed up to near the semiconductorstructure. Also, in the case where both the surface where the cleavagestarting portion 22 reaches and the surface to be pressed are disposedas the back surface BS of the substrate 5, unintended damage of thesemiconductor structure can be avoided, and the cleavage can beperformed with good yields.

Adhesive Sheet 50

In the case where the semiconductor wafer is divided into the pluralityof light-emitting elements, it is preferable that an adhesive sheet 50be arranged on a surface that is opposite side to the surface to bepressed of the main surfaces of the semiconductor wafer 20. Asillustrated in schematic cross-sectional views of FIGS. 6 and 9, theadhesive sheet 50 is applied in advance on the side of the first mainsurface 5 a (i.e., the side where the semiconductor structure 11 of thesemiconductor wafer 20 is arranged) of the substrate 5 and set on theupper surface of a receiving plate 40. With this arrangement, thesemiconductor wafer 20 is pressed against the adhesive sheet 50 with thepressing member 30, which allows singulated light-emitting elements tobe less likely to scatter. Also, pressing the semiconductor wafer 20against the adhesive sheet 50 can warp the semiconductor wafer 20 withuse of the repulsive force of the adhesive sheet 50. Accordingly, it ispossible to cleave the semiconductor wafer 20 in midair without pressingthe semiconductor wafer 20 against the surface of the receiving plate 40including a recess.

Such application of the adhesive sheet 50 may be performed prior orsubsequent to the formation of the cleavage starting portion 22, but isperformed before the cleavage. In the case where the cleavage startingportion 22 reaches the vicinity of the semiconductor structure, it ispreferable that the adhesive sheet 50 be applied prior to the formationof the cleavage starting portion 22, because if the adhesive sheet 50 isapplied subsequent to the formation of the cleavage starting portion 22,the semiconductor wafer 20 might be unintendedly singulated, and thelight-emitting elements might scatter.

Receiving Plate 40

In the example of FIG. 6, the semiconductor wafer 20 on which theadhesive sheet 50 is applied and including the cleavage starting portion22 is arranged on the receiving plate 40. Herein, the adhesive sheet 50is arranged on the surface of the receiving plate 40 in advance, and inthis state, the adhesive sheet 50 is applied on the semiconductor wafer20 so that the side on which the cleavage starting portion 22 is formedcorresponds to the surface to be pressed, that is, so that the side ofthe growth surface of the semiconductor structure faces the adhesivesheet 50, which allows for arrangement of the semiconductor wafer 20 onthe receiving plate 40. The aforementioned receiving plate 40 can bemade of, for example, stainless steel or zirconia. The diameter of thereceiving plate 40 is selected to be larger than the outer diameter ofthe semiconductor wafer 20. Such diameter allows the semiconductor wafer20 to be arranged on the receiving plate 40. With the arrangementdescribed above, the pressing member 30 is touched to the upper surfaceside of the semiconductor wafer 20 and pressed toward the receivingplate 40. The semiconductor wafer 20 being pressed is pressed on thesurface of the receiving plate 40 via the adhesive sheet 50 and bent atthe cleavage starting portion 22, which has low intensity, and thereforedivided along the cleavage starting portion 22. Concurrently, thepressing member 30 is scanned on the semiconductor wafer 20 in a statewhere the surface of the semiconductor wafer 20 to be pressed is pressedwith the pressing member 30, which allows for sequentially dividing thesemiconductor wafer 20 arranged on the receiving plate 40 into elements.The receiving plate 40 has a shaped depressed in the pressing direction(the downward direction in FIG. 6), and it is preferable that thedepressed surface thereof be a spherical surface of which the curvatureis lower than that of the tip portion 31. With this structure, thecentral vicinity of the tip portion 31 can be reliably pressed againstthe receiving plate 40. It is noted that, as described above, thesemiconductor wafer 20 can be cleaved without being pressed against thesurface of the receiving plate 40. In this case, the amount ofindentation into the semiconductor wafer 20 by the pressing member 30may be reduced to the extent that the semiconductor wafer 20 is notpressed against the receiving plate 40. With this arrangement, thedamage of the semiconductor wafer 20 can be reduced.

A base on which the semiconductor wafer 20 is arranged is not limited tothe receiving plate including the depression as illustrated in FIG. 6,but, for example, the semiconductor wafer 20 may be arranged on theupper surface of a flat base. In this case, cleaving the semiconductorwafer 20 with a relatively low amount of indentation is preferablebecause it can reduce the damage of the semiconductor wafer.

Protective Sheet 52

When the semiconductor wafer 20 is divided into the light-emittingelements, the protective sheet 52 may be arranged on the side of thesurface to be pressed of the main surfaces of the semiconductor wafer20. Such arrangement of the protective sheet 52 can prevent the pressingmember 30 from directly contacting the semiconductor wafer 20.Accordingly, damage of the semiconductor wafer 20 caused by the pressingmember 30 can be prevented, and damage of the tip portion 31 caused bythe fragment of the semiconductor wafer 20 also can be prevented.Furthermore, the lifting of the semiconductor wafer 20 at the time ofbeing pressed can be prevented, so that the effect of easy cleaving ofthe semiconductor wafer 20 can be expected. Also, in the case where amaterial having a low coefficient of dynamic friction is employed forthe protective sheet 52, the pressing member 30 can be smoothly slid onthe semiconductor wafer 20.

An example of arranging the protective sheet 52, as described above, isillustrated in a schematic cross-sectional view in FIG. 10 as a variantexample. As illustrated in this figure, the protective sheet 52 isarranged on the side of the surface to be pressed on the semiconductorwafer 20, and the semiconductor wafer 20 is set in a ring-shaped frame42 in a state where the adhesive sheet 50 is applied on the back surfaceBS of the semiconductor wafer 20. The size of the protective sheet 52 islarge enough to cover the whole of the semiconductor wafer 20. Also, theprotective sheet 52 is not required to be applied on the surface to bepressed, but may be applied on the adhesive sheet 50 in the periphery ofthe semiconductor wafer 20 in a state where the semiconductor wafer 20and the protective sheet 52 are overlapped. Also, for another mode, theprotective sheet 52 may be clamped with the ring-shaped frame 42 alongwith the adhesive sheet 50. For the protective sheet 52, sheet membersmade of resin, for example, made of PET, can be employed.

The ring-shaped frame 42 is formed in a frame shape in which the centralportion is opened so as to hold only the periphery of the semiconductorwafer 20. With such structure, the receiving plate for receiving the tipportion of the pressing member can be eliminated. However, as is thesame with FIG. 6 described above, the receiving plate can be arranged ata downward position corresponding to the tip portion of the pressingmember. In this case, the semiconductor wafer is held by the ring-shapedframe 42, so that it is not necessary to hold the semiconductor wafer bythe receiving plate, and the size of the receiving plate may be reducedin accordance with the size of the tip portion 31 of the pressingmember.

Scanning Pattern SP of Pressing Member 30

The pattern of scanning the pressing member 30 on the plane of thesemiconductor wafer 20 during the cleavage is preferably formed suchthat the pressing member 30 is transferred in the direction intersectingwith the entire straight lines including line segments forming thecleavage starting portion 22 in a plan view of the semiconductor wafer20. In other words, the pressing member 30 is scanned in the directionthat is not parallel to any side forming the polygon, which is the outershape of each light-emitting element. Such scanning has an advantagethat cleaving to obtain one light-emitting element can be accomplishedby one-time scanning on one light-emitting element using the pressingmember 30. More specifically, in the case where the semiconductor waferis cleaved into the background, rectangular light-emitting elements,scanning methods in which the pressing member is scanned in thelongitudinal direction or the lateral direction as illustrated in FIGS.13A and 13B have been used. However, these methods require scanning aplurality of times. In contrast, in the present embodiment, in order toperform cleaving to obtain one light-emitting element, scanning of onlyone time on one light-emitting is required. This is because, in thebackground cleaving method, the pressing member is scanned along a breakline (scribe line), and the break line is arranged in a lattice pattern,so that the scanning in the longitudinal direction and the lateraldirection is necessary. If this background method is applied to thepolygonal light-emitting elements, for example, hexagonal light-emittingelements in the present embodiment, the pattern of each cleavagestarting portion is a polygonal line, which may highly complicate thescanning pattern. Accordingly, in the present embodiment, the pressingmember 30 is scanned, intentionally, not along the a line segment of thecleavage starting portion 22. Conversely, as illustrated on the enlargedcross-sectional view in FIG. 11, the pressing member 30 is scanned inthe direction obliquely intersecting with the line segment of thecleavage starting portion 22 in a plan view. In this manner, stress isapplied to the line segment forming the cleavage starting portion 22arranged in various directions and angles, which allows for cleaving thesemiconductor wafer 20 at once. In particular, the tip portion 31 of thepressing member 30 is not a surface including edges, but a curvedsurface, which can easily disperse the stress from a point ofapplication and reduce the risks that the semiconductor wafer is cleavedin unintended directions at a location away from the cleavage startingportion 22. In this method, it is not necessary to scan the pressingmember 30 exactly along the break line as in the background method, andtherefore the control of scanning can be facilitated. Moreover, reducingthe number of times of scanning can lead to reduction in takt time andcan contribute to reduction in manufacturing costs of the light-emittingelements.

The direction of scanning the pressing member 30 can be, as illustratedin FIG. 11, for example, the direction that is inclined to theorientation flat surface OL of the semiconductor wafer 20. In this case,the inclination angle θ at which the pressing member 30 is scanned withrespect to the orientation flat surface OL, is selected to be an anglethat is not parallel to any side forming the outer shape of thelight-emitting element, that is, an angle at which the scanningdirection intersects with any side forming the outer shape of thelight-emitting element. For example, in the example in FIG. 11, theouter shape of the light-emitting element is a regular hexagon, and oneside (a side C in the diagram) of the regular hexagon is arranged to bein parallel with the orientation flat surface OL. Accordingly, when thepressing member 30 is scanned at an angle of 60 degrees with respect tothe orientation flat surface OL, the scanning direction corresponds tothe side A. As a result, stress concentrates on the side A, and while itis expected that the cleavage is sufficiently performed in this portion,it is considered that the stress of cleavage is relatively reduced inportions corresponding to other sides, which may cause unevenness inquality of the cleaved surfaces. Similarly, in the case where thepressing member 30 is scanned at an angle of 120 degrees with respect tothe orientation flat surface OL, the scanning direction corresponds tothe side B. Furthermore, in the case where the pressing member 30 isscanned at an angle of zero degrees with respect to the orientation flatsurface OL, that is, the scanning direction is not inclined, but inparallel with the orientation flat surface OL, the scanning directioncorresponds to the side C. Accordingly, in the example of FIG. 11, theinclination angle θ at which the pressing member 30 is scanned withrespect to the orientation flat surface OL, is selected to be an angleexcept for 0, 60, and 120 degrees.

In addition to the direction passing directly above each side of thepolygon, the direction passing vertically to the each side is consideredto be a pressing direction in which the semiconductor wafer 20 is easilycleaved. Accordingly, more preferably, the inclination angle of thepressing direction is determined so as to avoid the direction verticallyintersecting with each side. In the example in FIG. 11, in the casewhere the inclination angle θ is 30 degrees, the pressing direction isperpendicular to the side B, and in the case where the inclination angleθ is 90 degrees, the pressing direction is perpendicular to the side C,and in the case where the inclination angle θ is 150 degrees, thepressing direction is perpendicular to the side A. Accordingly, it ispreferable that the inclination angle θ not be 30, 90, or 150 degrees.In other words, in the case where the light-emitting element has a shapeof a regular hexagon, it is preferable that the inclination angle θ ofthe scanning direction of the pressing member 30 is selected to be anangle that excludes a multiple of 30 degrees with respect to theorientation flat surface OL. In view of this, more preferably, theinclination angle θ is selected from the vicinity of angles of 15, 45,75, 105, 135, and 165 degrees, each of which is in the middle of rangeof the angles excluding a multiple of 30 degrees. In this manner,uniform stress is applied to each side of the regular hexagon of theshape of the light-emitting element, and therefore it is expected thatquality in the cleaved surface of each side is uniformed. In the exampleillustrated in FIG. 11, the inclination angle θ is 45 degrees.

As described above, scanning the pressing member 30 so that the scanningdirection does not correspond to the direction of each side of thelight-emitting element and/or the direction vertically intersecting witheach side of the light-emitting element can uniform easiness of cleavageof each side. As a result, the state of cleavage in the surface of thesemiconductor wafer can be uniformed.

It is preferable that intervals D_(S) between scanning patterns SP beselected so that all the light-emitting elements included in thesemiconductor wafer 20 are singulated. An area being pressed by one-timelinear scanning is determined in accordance with the shape and theamount of indentation by the tip portion 31, in view of which theintervals D_(S) between the scanning patterns SP can be selected. It ispreferable that the intervals D_(S) between the scanning patterns SP beequal to or less than the maximum width of the area that the tip portion31 can press, and more preferably less than the maximum width of thearea that the tip portion 31 can press. The scanning patterns SP of thepressing member 30 refer to a locus through which the center of the tipportion 31 passes.

In the description above, the case in which the orientation flat surfaceOL and one of sides of the light-emitting element are parallel to eachother has been exemplified. With the aforementioned arrangement, thescanning direction can be defined based on the orientation flat surfaceOL. However, the present disclosure is not limited to this. For example,all sides of the light-emitting element in plan view are not parallel tothe orientation flat surface OL. In this case, similarly to the exampledescribed above, it is preferable that the pressing member 30 scans onthe semiconductor wafer at an angle at which the scanning directionintersects with all the straight lines including the sides of thelight-emitting element, and more preferably, the pressing direction isselected so that the scanning direction does not correspond to thedirection vertically intersecting with each side of the light-emittingelement.

Extracting Light-emitting Element

After the light-emitting elements are divided, each light-emittingelement is taken out in Step S24 in FIG. 2. In the example illustratedin the cross-sectional view in FIG. 10, each light-emitting element isheld in a state of being stuck with the adhesive sheet 50. With thisarrangement, from a state where each light-emitting element has cleavedalong the cleavage starting portion 22, each light-emitting element isseparated from the adhesive sheet 50, so that singulated light-emittingelement can be obtained.

SECOND EMBODIMENT

In the first embodiment described above, the scanning pattern SP of thepressing member 30 is constituted of linear transfer of the pressingmember 30. That is, as illustrated in FIG. 11, the pressing member 30 isreciprocated in the direction inclined at the inclination angle θ withrespect to the orientation flat surface OL of the semiconductor wafer20. However, the locus of scanning of the pressing member 30 is notlimited to this, but the scanning patterns, with which any areacorresponding to each light-emitting element can be pressed, may beemployed. For example, the pressing member 30 can be scanned in a spiralform such that a circle is drawn from the central portion to the outercircumferential portion of the semiconductor wafer.

A method for manufacturing the light-emitting element according to asecond embodiment, the example of a pattern SP′, in which the pressingmember is scanned in a spiral form, is illustrated in a schematic planview in FIG. 12. This method has an advantage that control of transferof the pressing member can be successively and smoothly performed,compared with the case where the pressing member is linearly transferredas illustrated in FIG. 11. That is, in the case of the scanning patternsSP in which the pressing member is linearly transferred as illustratedin FIG. 11, the pressing member is temporarily stopped at the startpoint and the end point of the straight line, and accordingly the cycleof stopping and moving is repeated. Accordingly, due to inertia, thetransfer velocity of the pressing member is reduced in the vicinity of aposition at which the pressing member stops, which leads to thenon-uniformity of scanning velocity at each section. Accordingly, thetransfer velocity of the pressing member is relatively reduced in thevicinity of the position at which the pressing member stops, which leadsto a state where the semiconductor wafer is pressed in a longer time. Inother words, it is considered that, at a portion near the periphery ofthe semiconductor wafer, where the pressing member is stopped,unevenness in the results of the cleavage occurs compared with thecentral region of the wafer. In contrast, in the case of the patternSP′, in which the pressing member is scanned in a spiral form, thepressing member is easily transferred in a continuous manner, and thescanning velocity can be easily approximated to a constant velocity.Accordingly, an advantage that uniform pressing pressure can be appliedto each light-emitting element can be obtained, and the takt time can bereduced.

Thus, the scanning pattern of the pressing portion is not limited to thelinear form, but the curved line can be employed. That is, the pressingportion is scanned on the surface of the semiconductor wafer 20 in asingle movement, which can form the scanning pattern in which the locusof scanning is included in any area corresponding to each light-emittingelement. It is noted that the second embodiment is similar to the firstembodiment except for the difference in the scanning patterns of thepressing member.

The embodiments, examples, and modifications of the present disclosurehave been described based on the drawings above. However, theembodiments or examples, and modifications described above are providedfor the purpose of embodying the technical concept disclosed in thepresent disclosure, and the present disclosure is not limited to thedescriptions above. Also, in the present specification, the membersdisclosed in the claims are not limited to the members specified in theembodiments. Unless otherwise specifically stated, the scope of thepresent disclosure is not limited to the descriptions in theembodiments, and in particular, size, material, shape, and relativearrangement of members described in the embodiments are given asexamples. It is noted that the sizes or positional relation ofrespective members illustrated in each diagram may be exaggerated so asto clarify the descriptions. Furthermore, in the description above, thesame designations or the same reference numerals denote the same orsimilar member, and its detailed description is appropriately omitted.In addition, a plurality of structural elements of the presentdisclosure may be configured as a single part which serves the purposeof a plurality of elements; on the other hand, a single structuralelement may be configured as a plurality of parts which serve thepurpose of a single element.

The light-emitting element obtained by the method described above can beutilized for light sources for illuminating devices, LED displays, lightsources for backlight, traffic signal devices, lighting switches,various display devices such as advertisements or destination guide,image reading devices such as digital video cameras, facsimile machines,copying machines, and scanners, projector devices, or the like. Themethod described above can be applied to not only the semiconductorlight-emitting elements such as LEDs used for various sensors andindicators, but also to the manufacturing of other semiconductorelements, for example, such as light receiving elements and amplifierelements.

What is claimed is:
 1. A method for manufacturing a semiconductorelement, comprising: providing a semiconductor wafer including asubstrate and a semiconductor structure on the substrate; forming acleavage starting portion in the semiconductor wafer; and dividing thesemiconductor wafer into a plurality of semiconductor elements bytransferring a pressing member on the semiconductor wafer in a statewhere the pressing member is pressed against the semiconductor wafer toseparate the semiconductor wafer at the cleavage starting portion,wherein the pressing member includes a tip portion to be pressed on thesemiconductor wafer, the tip portion has a spherical surface, and eachof the plurality of semiconductor elements has a shape of a polygonhaving five or more angles in a plan view.
 2. The method formanufacturing the semiconductor element according to claim 1, whereinthe dividing the semiconductor wafer into the semiconductor elementscomprises scanning the pressing member on the semiconductor wafer in adirection that is not parallel to any side forming an outer shape of thepolygon of each semiconductor element in the plan view.
 3. The methodfor manufacturing the semiconductor element according to claim 2,wherein the dividing the semiconductor wafer into the semiconductorelements comprises scanning the pressing member linearly.
 4. The methodfor manufacturing the semiconductor element according to claim 1,wherein the dividing the semiconductor wafer into the semiconductorelements comprises scanning the pressing member on the semiconductorwafer in a direction inclined with respect to an orientation flatsurface of the semiconductor wafer in the plan view.
 5. The method formanufacturing the semiconductor element according to claim 1, wherein anouter shape of the tip portion is longer than a diameter of acircumscribed circle of the shape of the semiconductor element in theplan view.
 6. The method for manufacturing the semiconductor elementaccording to claim 5, wherein the outer shape of the tip portion is twotimes or more as long as the diameter of the circumscribed circle of theshape of the semiconductor element in the plan view.
 7. The method formanufacturing the semiconductor element according to claim 1, wherein,before the dividing the semiconductor wafer into the semiconductorelements, the cleavage starting portion reaches a surface of thesemiconductor wafer to be pressed with the pressing member.
 8. Themethod for manufacturing the semiconductor element according to claim 1,wherein, before the dividing the semiconductor wafer into thesemiconductor elements, the cleavage starting portion is formed to reacha surface of the substrate on a side opposite to a surface of thesubstrate on which the semiconductor structure is formed.
 9. The methodfor manufacturing the semiconductor element according to claim 8,wherein, before the dividing the semiconductor wafer into thesemiconductor elements, the cleavage starting portion is formed up to besubstantially near the semiconductor structure on the substrate.
 10. Themethod for manufacturing the semiconductor element according to claim 1,wherein, in the dividing the semiconductor wafer into the semiconductorelements, a surface of the semiconductor wafer, on an opposite side withrespect to a surface of the semiconductor wafer to be pressed with thepressing member, is fixed to an adhesive sheet.
 11. The method formanufacturing the semiconductor element according to claim 10, wherein,in the dividing the semiconductor wafer into the semiconductor elements,the semiconductor wafer is cut and separated at the cleavage startingportion in midair and divided into the individual semiconductorelements.
 12. The method for manufacturing the semiconductor elementaccording to claim 1, wherein the cleavage starting portion is formed ina bent polygonal line in the plan view.
 13. The method for manufacturingthe semiconductor element according to claim 1, wherein the cleavagestarting portion is formed by focusing a laser beam in an interior ofthe substrate.
 14. The method for manufacturing the semiconductorelement according to claim 1, wherein the substrate has a crystalstructure of a hexagonal crystal system, and the shape of eachsemiconductor element in the plan view is a hexagon.
 15. The method formanufacturing the semiconductor element according to claim 1, whereinthe dividing the semiconductor wafer into the semiconductor elementscomprises scanning the pressing member on the semiconductor wafer so asto reciprocate in a direction inclined with respect to an orientationflat surface of the semiconductor wafer in the plan view.
 16. A methodfor manufacturing a semiconductor element, comprising: providing asemiconductor wafer including a substrate and a semiconductor structureon a first main surface of the substrate; forming a cleavage startingportion in the semiconductor wafer, the cleavage starting portion beingformed to reach a second main surface of the substrate on an oppositeside with respect to the first main surface; and dividing thesemiconductor wafer into a plurality of semiconductor elements bytransferring a pressing member on the semiconductor wafer in a statewhere the pressing member is pressed on the second main surface toseparate the semiconductor wafer at the cleavage starting portion,wherein the pressing member includes a tip portion to be pressed on thesemiconductor wafer, the tip portion has a curved surface, and each ofthe plurality of semiconductor elements has a shape of a polygon havingfive or more angles in a plan view.
 17. A method for manufacturing asemiconductor element, comprising: providing a semiconductor waferincluding a substrate and a semiconductor structure on the substrate;forming a cleavage starting portion in the semiconductor wafer; anddividing the semiconductor wafer into a plurality of semiconductorelements, each semiconductor element having a shape of a polygon havingfive or more angles in a plan view, by transferring a pressing member onthe semiconductor wafer so that the pressing member scans linearly in adirection that is not parallel to any side forming an outer shape of thepolygon of each semiconductor element, in a state where the pressingmember is pressed against the semiconductor wafer to separate thesemiconductor wafer at the cleavage starting portion, wherein thepressing member includes a tip portion to be pressed on thesemiconductor wafer, and the tip portion has a curved surface.